These are checked when an order changes and again on the day a reminder is due.
- Already reordered. A new paid order for the same product skips the older reminder, matched by account and billing email, in any letter case. The new order starts its own clock. If that new order is later cancelled or refunded, the old reminder comes back.
- Not available. Out of stock, deleted or not for sale.
- Refunded or cancelled. The order behind the reminder is gone.
- Days between reminders. Reminders due too soon after the last one wait.
